Open the key fob by prying the two halves apart
The Mazda CX-5 key fob splits into two plastic halves held together by a small slot. Look for a thin seam running around the edge of the fob—this is where the two pieces meet. Insert a flat tool (a coin, flathead screwdriver, or plastic pry tool works) into that seam and gently twist to separate the halves. You do not need force; the fob is designed to come apart this way.
Once you have created a small gap, you can usually work your fingers into the opening and pull the halves apart by hand. Be careful not to lose the small spring or contact plate inside—these are straightforward to drop and harder to find on a floor. Set one half aside on a clean surface where you can see all the pieces.
Key Takeaways
- Mazda CX-5 key fobs use a CR2032 battery, which you can buy at any pharmacy, grocery store, or hardware store for a few dollars.
- The battery slides out of a metal holder on the circuit board; note which side faces up before you remove it so you can install the new one the same way.
- The fob splits at a seam around its edge—use a coin or plastic tool to pry gently rather than force.
- Reassemble the fob by pressing the two halves together until they click, and test all buttons before you put the fob back in your pocket.
Identify and remove the old CR2032 battery
Inside the fob you will see a small circular battery held in a metal clip or spring holder on the circuit board. This is a CR2032 battery, a common coin-cell type about the size of a dime. Before you remove it, look at which side is facing up—the positive (+) side or the negative (−) side. You need to install the new battery the same way.
Slide the old battery out of its holder by gently pushing it to one side. If it is stuck, a small plastic pry tool or the edge of a coin can help you lift it without bending the metal clip. Once the battery is out, set it aside and inspect the metal holder to make sure it is not bent or corroded. If the contacts look dirty, you can gently wipe them with a dry cloth.
Insert the new CR2032 battery with the correct orientation
Buy a replacement CR2032 battery from a pharmacy, grocery store, hardware store, or online retailer. They cost between two and five dollars. Remove the battery from its packaging and check that the positive (+) side matches the orientation you noted from the old battery. Slide the new battery into the metal holder, making sure it sits flat and the clip holds it securely.
Press gently on the battery to confirm it is seated properly. You should hear or feel a small click as the metal clip grips the battery. If the battery sits loose or tilts, remove it and try again—a loose battery will not make contact and the fob will not work.
Reassemble the two halves of the fob
Line up the two plastic halves so the seam is even all the way around. Press them together firmly until you hear or feel a click—this means the clips have engaged and the fob is sealed. Start at one end and work your way around if the halves do not snap together smoothly all at once.
Once the fob is closed, hold it in your hand and make sure there are no gaps between the halves. If you see a gap, the battery or internal parts may be preventing a clean seal. Open the fob again, check that the battery is seated correctly, and try reassembling.
Test the key fob before you rely on it
Stand near your CX-5 and press each button on the fob—lock, unlock, panic, and trunk release if your model has one. You should see the lights on your vehicle respond, and you should hear the locks engage or disengage. If nothing happens, open the fob again and check that the battery is installed with the correct side facing up.
If the buttons still do not work after you have checked the battery orientation, the battery may be defective or the fob itself may need service. Try a different new battery first. If that does not solve the problem, contact a Mazda dealer or a locksmith who works on car key fobs.
What to do if the fob still does not work after battery replacement
A fob that does not respond after a fresh battery usually has one of three problems: the battery is installed upside down, the battery contacts inside the fob are corroded or dirty, or the fob's circuit board is damaged. Start by opening the fob again and double-checking the battery orientation against the markings inside the holder.
If the orientation is correct, remove the battery and inspect the metal contacts for dirt, corrosion, or discoloration. A white or green coating on the contacts means corrosion has built up. Clean the contacts gently with a dry cloth or a pencil eraser, then reinstall the battery. If the fob still does not work, the circuit board may be damaged and the fob will need to be replaced or repaired by a Mazda dealer or professional locksmith.
Frequently Asked Questions
Where can I buy a CR2032 battery?
CR2032 batteries are sold at pharmacies, grocery stores, hardware stores, big-box retailers, and online. They are inexpensive—usually between two and five dollars—and you do not need to order them; most stores stock them in the electronics or battery aisle.
Can I use a different battery size in my Mazda key fob?
No. The CR2032 is the correct size for a Mazda CX-5 fob. Other battery sizes will not fit the holder or will not make proper contact. Always use a CR2032.
How often do I need to replace the battery?
A CR2032 battery typically lasts three to four years in a key fob, depending on how often you use it. When the buttons become slow to respond or stop working, it is time to replace the battery.
What if I drop a screw or spring while the fob is open?
Most Mazda CX-5 fobs do not have screws—they are held together by clips. If you do lose a small part, check the surface where you were working and use a flashlight to look for it. If you cannot find it, contact a Mazda dealer or locksmith; they can order replacement parts or repair the fob.
Do I need to reprogram my key fob after changing the battery?
No. Changing the battery does not erase the fob's programming. Once you install the new battery and reassemble the fob, it should work when ready without any reprogramming.